Encyclopedia

of Home Improvements

*Where to Insulate in a Home*

For energy efficiency, your home should be properly insulated from the roof down to its foundation. This includes the following areas:
Seal all attic-to-home air leaks. Most insulation does not stop airflow.

Duct exhaust fans to the outside. Use a tightly constructed box to cover fan housing on attic side. Seal around the duct where it exits the box. Seal the perimeter of the box to the drywall on attic side.

Cover openings-such as dropped ceilings, soffits, and bulkheads-into attic area with plywood and seal to the attic side of the ceiling.

Seal around chimney and framing with a high-temperature caulk or furnace cement.

At the tops of interior walls, use long-life caulk to seal the smaller gaps and holes. Use expanding foam or strips of rigid foam board insulation for the larger gaps.

Install blocking (metal flashing) to maintain fire-safety clearance requirements (usually 3 inches) for heat-producing equipment found in an attic, such as flues, chimneys, exhaust fans, and light housings/fixtures unless the light fixtures are IC (insulation contact) rated. IC-rated lights are airtight and can be covered with insulation.

Make sure insulation doesn't block soffit vents to allow for attic ventilation.

Check the attic ceiling for water stains or marks. They indicate roof leaks or lack of ventilation. Make repairs before you insulate. Wet insulation is ineffective and can damage your home.

When insulating a conditioned basement, only the walls need to be insulated. The basement ceiling may be insulated for noise control between floors. "Conditioned" means the space is heated or cooled by a furnace or air conditioning unit.

1.Before insulating begins, a ventilation baffle should be installed at the eave of every joist, to make sure the ventilation space is not blocked by insulation

2. To install the insulation, push the material up between the rafters until it's flush with the edge of the wood. If a faced insulation product is being used, the facing goes toward the inside of the house -- the warm side in heating climates. At least one inch of ventilation space is required between the insulation and the roof deck. Some local codes require even more vent space, so find out what's called for in your area.. If a standard insulation batt is being used, or if the code requires more vent space, install ventilation baffles along the entire run of each rafter cavity in order to ensure a vented installation.

3. Insulation should be kept three inches away from recessed lighting fixtures unless the fixture is marked "I.C." (Insulated Ceiling), which is designed for direct contact with the insulation. If insulation is placed over an unrated fixture, it may cause the fixture to overheat and perhaps start a fire. Also, the insulation should always be installed at least three inches away from any metal chimneys, gas water heater flues or other heat-producing devices.

Always install the insulation with the vapor retarder toward the warm side of the structure in heating climates. In a vented crawlspace, the warm side is usually up, closest to the floor

The insulation should be installed all the way back at the end of each joist run so that it touches the band joist. You want complete coverage under the house. There will usually be a narrow joist space on the walls that runs parallel to the joist. The insulation should be cut to fit this space.

There are often both pipes and wires in crawlspace floors and occasionally a junction box. Water pipes should be insulated and you will need to insulate carefully around electrical wiring and boxes.
Insulation should be placed around cross braces by cutting it and pushing it between the

Once the insulation is in place between the floor joists, insulation hangers or nylon straps can be used to hold the product in place.
A 4- or 6-mil. polyethylene vapor retarder should be laid down to completely cover the ground. Place rocks or bricks around the perimeter to hold it in place.

1. For standard wall heights, use pre-cut batts rather than continuous rolls. Each piece of insulation is manufactured to the size of the most typical framing, which usually is built either 16 or 24 inches on center and about 92 inches high. These cut-to-size batts will make the job go faster and easier

2. The insulation should fit snug against the studs and completely fill the cavity to the top and bottom plates. Cut batt insulation to fit snugly around obstructions such as electrical boxes, plumbing and plumbing vent lines.

3. When using kraft-faced batts with flanges, staple the flanges every 8 - 12 inches. The flanges can be stapled to the front or inside of the stud. Drywall installers prefer the facing to be stapled on the inside of the studs. Owens Corning PROPINK FastBatt™ Insulation does not have stapling.

Note: Never leave faced insulation exposed. The facings on Kraft-and-foil-faced insulation will burn and must be installed in substantial contact with an approved ceiling, wall or construction material to help prevent the spread of fire in the wall, ceiling or floor cavities. Unfaced fiber glass is non-combustible

In heating climates, homes with subfloors of plywood or OSB sheathing generally will not need a separate vapor retarder. But older homes with sub-floors made of wood planking may need a separate vapor retarder. (In Gulf Coast and Florida, local building practice may not call for any interior vapor retarder.) If needed, simply cut strips of polyethylene the width of joists and staple directly to underside of subfloor, or use kraft-faced insulation with the paper up and in contact with the

Begin at one end of floor and place insulation between floor joists.
Insulation will stay in place temporarily if you are using R-19. R-25 insulation needs to be supported as you go. Use metal insulation supports (16" or 24" wire rods or crisscrossed wire) to hold insulation in place. Be careful not to compress insulation too much with supports. Insulation should fit snugly against band joist and overlap bottom plate.

Measure and cut small pieces of unfaced insulation to fit snugly against band joist. If the insulation is faced, peel off facing before installing the small pieces. Where a wall vapor retarder is required, use a material that meets local building codes (fire rated).

1. Lay temporary flooring (using plank or plywood pieces) across joists and hang a temporary work light. To make sure the eave vents aren't blocked, Owens Corning Raft-R-Mate® attic vents or baffles should be installed to provide unobstructed air

2. Begin laying faced fiber glass insulation at outer edge of attic and work toward center. The vapor retarder should be facing down toward the warm-in-winter (living area) side of the ceiling. In Gulf Coast states and Florida, local building practice may not call for an interior vapor retarder.

3. Lay in long runs first and use leftovers for shorter spaces. Ends of insulation should be cut to fit snugly around cross bracing. Insulation should extend far enough to cover exterior walls but should not block flow of air from eave vents. If needed, install a baffle wherever there is an eave vent to assure air flow. For additional

4. Insulation must be kept three inches away from recessed lighting fixtures unless fixture is marked "I.C." (Insulated Ceiling) - designed for direct insulation contact. The facing should be cut back so it is not touching the light fixture. Insulation placed over an unrated fixture may cause it to overheat and start a fire. The insulation should always be installed at least three inches away from any metal chimneys, gas water heater flues or other heat-producing devices.

5. Fill the spaces between a masonry chimney and wood framing with a non-combustible material such as unfaced fiber glass insulation, which will not burn

Duct Insulation

Properly insulating air ducts located in unconditioned spaces such as attics, crawl spaces, garages, or unfinished basements can help improve your home's energy efficiency.

Air ducts supply conditioned air from your space heating and cooling equipment to your living spaces. They also return an equal volume of air back to the equipment to be conditioned again.
Ducts are typically made out of thin metal materials that easily conduct heat. Therefore, uninsulated or poorly insulated ducts in unconditioned spaces can lose through conduction 10%-30% of the energy used to heat and cool your home. The heating and cooling equipment then has to compensate for the heat loss and gain by conditioning additional air. This added conditioning raises a homeowner's energy bills. In addition, when ducts lose heat through conduction, rooms served by long duct runs can experience "cold blow" during the winter because they usually have lower heating-supply temperatures.

Ducts in conditioned spaces experience minimal conductive losses and gains since they are exposed to indoor air temperatures. However, these ducts may also require some insulation to prevent condensation on duct walls and to ensure that conditioned air is delivered at the desired temperature.

Back to Topics Page

Contact